Synchronizing mechanism

ABSTRACT

A synchronizing mechanism for the correlated movement of the seat and backrest assembly of an office chair has a basic carrier capable of being positioned on the chair upright, a seat carrier and a backrest carrier. The backrest carrier is capable of pivoting about a transverse shaft and is connected directly in an articulated fashion both to the basic carrier and to the rear end area of the seat carrier such that a pivoting movement of the backrest in a rearward direction induces a lowering movement in the rearward area of the seat carrier. The seat carrier is connected in an articulated fashion to the basic carrier such that a horizontal sliding movement towards the rear is superimposed on the lowering movement of the seat carrier. Through the direct linking of the backrest carrier to the basic carrier and the seat carrier, it is possible to simplify the construction.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit under 35 U.S.C. §119 (e), of copending U.S. Provisional Application No. 60/646,279, filed Jan. 24, 2005; this application also claims the priority, under 35 U.S.C. §119, of German patent application No. 10 2005 003 383.0, filed Jan. 24, 2005; the prior applications are herewith incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The invention relates to a synchronizing mechanism for the correlated movement of a seat and backrest assembly of an office chair. The synchronizing mechanism has a basic carrier capable of being positioned on a chair upright, a seat or seat carrier and a backrest carrier.

The designation “synchronizing mechanism” is understood to denote assemblies in the substructure of the seat of an office chair, which assemblies ensure an interconnected kinematic effect with an associated specific relative movement of the seat and the backrest in relation to one another. Positioned for this purpose on a chair upright is a basic carrier, on which are mounted on the one hand a seat carrier, capable of pivoting about a transverse shaft and attached to the basic carrier in an articulated fashion, and on the other hand a backrest carrier, similarly capable of pivoting about a transverse shaft and attached to the basic carrier in an articulated fashion. The seat of the office chair, which is provided as a general rule with an upholstered seat surface, is mounted on the seat carrier. The backrest carrier, which usually extends rearwards from the actual synchronizing mechanism, carries the backrest of the office chair on an upward-extending bracket.

The seat carrier and the backrest carrier are connected together in an articulated fashion in such a way that a pivoting movement of the backrest in a rearward direction as may be brought about, for example, by the action of the user of the chair leaning against the backrest will induce a lowering movement of the rear edge of the seat in a downward direction. This correlated movement of the seat and backrest assembly is associated with a significant comfort-related benefit and is desirable for orthopedic reasons.

A synchronizing mechanism of this kind was previously disclosed in published, non-prosecuted German patent application DE 101 25 994 A1 (corresponding to U.S. Pat. No. 6,675,774). The seat carrier in this case is connected to the basic carrier via a linkage arrangement having a complicated configuration in the form of a four-bar chain. A comparatively large pivoting angle for the backrest is achieved in this way. Furthermore, a comparatively large lowering movement of the seat surface is also achieved through this solution, including at a relatively large pivoting angle of the backrest, as the seat carrier and the backrest carrier are pivotally mounted at several points on the basic carrier.

SUMMARY OF THE INVENTION

It is accordingly an object of the invention to provide a synchronizing mechanism that overcomes the above-mentioned disadvantages of the prior art devices of this general type, which is simple to construct.

With the foregoing and other objects in view there is provided, in accordance with the invention, a synchronizing mechanism for correlating a movement of a seat and a backrest assembly of an office chair. The synchronizing mechanism contains a seat carrier having a rear end area, a first transverse shaft, a basic carrier capable of being positioned on the office chair upright, and a backrest carrier capable of pivoting about the transverse shaft and is connected directly in an articulated fashion to the basic carrier and to the rear end area of the seat carrier such that a pivoting movement of the backrest carrier in a rearward direction will induce a lowering movement in the rear end area of the seat carrier. The seat carrier is capable of pivoting about a second transverse shaft and is connected directly to the basic carrier in an articulated fashion such that a horizontal sliding movement towards a rear is superimposed during the lowering movement of the seat carrier.

According to the invention, the backrest carrier, which is pivotally mounted about a transverse shaft, is connected directly in an articulated fashion both to the basic carrier and to the rear end area of the seat or the seat carrier, so that a pivoting movement of the backrest towards the rear induces a lowering movement of the rearward areas of the seat carrier. In addition, the seat or the seat carrier, which is similarly pivotally mounted about a transverse shaft, is also connected to the basic carrier in an articulated fashion, so that a horizontal sliding movement towards the rear is superimposed on the lowering movement of the seat carrier. Through the direct linking of the backrest carrier to the basic carrier and the seat or the seat carrier, it is possible to simplify the construction of the synchronizing mechanism significantly. A complicated linkage configuration, for example in the form of a four-bar chain, can now be dispensed with. Nevertheless, thanks to the configuration of the synchronizing mechanism in accordance with the invention, the achievable seating comfort is comparable with that of the synchronizing mechanism of a more complicated construction. A configuration in which a ratio of a horizontal component of an articulation distance to a vertical component of the articulation distance lies between 0.6 and 1.7 has been found to be advantageous. A ratio of between 1.0 and 1.2 is particularly advantageous. It has been found to be advantageous, in addition, if the ratio of the horizontal component of the articulation distance to the vertical component of the articulation distance lies between 2.8 and 5.8 in the maximum rearward-pivoted position. A ratio of between 3.5 and 3.9 is particularly advantageous. It is also of advantage, furthermore, if the ratio of a lowering angle of the seat or the seat carrier to a pivoting angle of the backrest carrier lies between 1:2.1 and 1:3.0 in the maximum rearward-pivoted position. A ratio of between 2.5 and 2.7 is particularly advantageous. These embodiments permit the particularly comfortable pivoting of the seat.

It is also particularly advantageous, furthermore, if the connection of the seat or the seat carrier to the basic carrier is effected via a rotary sliding articulation. The horizontal sliding movement of the seat or the seat carrier towards the rear can thus be achieved in a particularly easy and robust fashion.

In a further advantageous embodiment of the invention, a stop mechanism disposed in the front area of the seat is provided for locking the position of the seat carrier relative to the basic carrier. The operating convenience of the synchronizing mechanism is further increased in this way. Where intermediate stages are provided for the locking function, the seat can be fixed in a simple manner in various inclined positions.

Automatic variation of the “resistance to pivoting” of the backrest is possible if a spring configuration is provided for pre-tensioning the synchronizing mechanism, in conjunction with which the spring configuration contains a leg spring, one leg of which abuts against a counterpart disposed on the seat or the seat carrier in such a way that the position of the articulation point, and thus the spring characteristic of the leg spring, is varied in conjunction with the pivoting of the backrest. Particularly light setting of the pre-tensioning of the synchronizing mechanism is possible, finally, if a worm gear is provided for actuation of an adjustment mechanism for the leg spring.

Other features which are considered as characteristic for the invention are set forth in the appended claims.

Although the invention is illustrated and described herein as embodied in a synchronizing mechanism, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.

The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic, side view of a synchronizing mechanism in a basic position according to invention;

FIG. 2 is a diagrammatic, side view of the synchronizing mechanism in a position pivoted rearwards to its maximum extent;

FIG. 3 is a diagrammatic, front view of the synchronizing mechanism;

FIG. 4 is a diagrammatic, sectional view taken along the line IV-IV shown in FIG. 3;

FIG. 5 is a diagrammatic, sectional view taken along the line V-V shown in FIG. 3;

FIG. 6 is a diagrammatic, sectional view taken along the line VI-VI shown in FIG. 1; and

FIG. 7 is a diagrammatic, sectional view taken along the line VII-VII shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the figures of the drawing in detail and first, particularly, to FIG. 1 thereof, there is shown a synchronizing mechanism 1 having a basic carrier 2, which is located at an upper end of a chair upright by use of a conical seat 3, as also represented in published, non-prosecuted German patent application DE 101 25 944 A1 (corresponding to U.S. patent publication No. 2002/0171276 A1). The synchronizing mechanism 1 is formed of a frame-shaped seat carrier 4 and a backrest carrier 5 that is stirrup-shaped in plan view, the side pieces 6, 7 of which are disposed to either side of the basic carrier 2.

A seat is provided with a non-illustrated upholstered seat surface and is mounted on the seat carrier 4. Guide elements 9 with a T-shaped cross section, which are used for the longitudinal displacement of the seat, are disposed for this purpose on an upper side 8 of the seat carrier 4. It is also possible, of course, to use a seat that is rigidly connected to the seat carrier 4. If a seat that is capable of displacement relative to the seat carrier 4 is used, the position of the seat can be adjusted at the factory in a simple fashion by changing the position of the guide elements 9 on the seat carrier 4, and in a particularly simple fashion, for example, by screwing the guide elements in a different position on the seat carrier 4. A number of locking projections 11 disposed one after the other in the longitudinal direction L of the chair are provided on a lateral frame elements 10 of the seat carrier 4, which locking projections also serve for the positioning and attachment of the seat on the seat carrier 4 in a previously disclosed fashion that is not explained here in any greater detail.

Attached to the backrest carrier 5 is a backrest, not represented here in any greater detail, which is capable of vertical adjustment in modern office chairs. The backrest can also be attached to the backrest carrier 5 in a single piece.

As is shown particularly clearly in FIG. 3, the entire synchronizing mechanism 1 is constructed with axial symmetry with regard to a central longitudinal plane M, which affects the actual kinematics. In this respect, it should be assumed that pairs of structural elements present on both sides of the actual synchronizing mechanism 1 are always intended in the following description.

On the one hand, the backrest carrier 5 is attached in an articulated fashion directly to the basic carrier 2 by the lower, forward-facing end 12 of the side piece 6. In the illustrative embodiment, the forward-facing or lower end 12 of the side piece 6 is mounted on a pivot bearing 13 on the basic carrier 2 in such a way that the backrest carrier 5 is articulated directly via the pivot bearing 13 more or less centrally on the basic carrier 2. In this way, the backrest carrier 5 can be caused to pivot with the backrest in the direction of pivoting S about a pivot shaft 14 running through the pivot bearing 13. An additional connecting element, for example an intermediate articulation between the backrest carrier 5 and the basic carrier 2, is not provided.

On the other hand, the backrest carrier 5 is attached to an upper end 15 of the side piece 6 via an articulation 16 to the seat carrier 4 in its rear end area 17. By causing the backrest to pivot, the seat carrier 4 is also carried in the direction of pivoting S and is lowered. In other words, pivoting takes place about a pivot shaft 19 of the articulation 16.

With the backrest carrier 5 in the basic position shown in FIG. 1, a longitudinal axis 18 of the pivoting mechanism passing through the articulation points 13, 16 runs at a steeply rearward-inclined angle. In the basic position, the ratio of a horizontal component x of an articulation distance A to a vertical component y of the articulation distance A is of the order of 1.1. The longitudinal axis 18 in this case includes an angle W1 of rather more than 40° with a plane E of the seat carrier lying substantially horizontally in the basic position.

In a maximum, rearward-pivoted position, the linkage is inclined even further to the rear; see FIG. 2. The ratio of the horizontal component x of the articulation distance A to the vertical component y of the articulation distance A is then of the order of 3.7. An angle W2 between the longitudinal axis 18 and the plane E of the seat carrier is less than 26°.

Because of the geometry of the pivoting mechanism, which is determined essentially by the articulation distance A and the angle W between the longitudinal axis 18 and the plane E of the backrest, a transmission ratio of approximately 1:2.6 is achieved in the maximum, rearward-pivoted position.

Therefore, for a lowering angle of the seat carrier 4 of approximately 10°, the backrest carrier 5 will be caused to pivot rearwards thorough a pivot angle of approximately 26°; see FIG. 2. The geometry that is used has the advantage that a large lowering angle of the seat carrier 4 can be achieved without the pivot angle of the backrest having to be too large, which would lead to a position resembling a reclining position. The so-called “shirt-pulling-out effect” is also effectively avoided in this way.

The front view represented in FIG. 3 illustrates schematically the position of the sectioned views. Both a section (FIG. 5) along the central plane M and a further section (FIG. 4) along a laterally displaced plane running parallel with the plane M are shown.

As illustrated in FIG. 4, the seat carrier 4 is connected in its front end area 21 to the basic carrier 2 via a rotary sliding articulation 22. The sliding articulation contains a sliding element 23 connected to the seat carrier 4, which sliding element 23 engages in a slideway formed by two sliding blocks 24, 25 disposed at a mutual distance from one another, which sliding blocks 24, 25 securely attached to the basic carrier 2. In the basic position illustrated here, the upper sliding block 25 makes contact with a stop 26 on the seat carrier 4. The seat carrier 4 is prevented in this way from executing a pivoting movement in a forward direction extending beyond the substantially horizontal basic position. Both of the sliding blocks 24, 25 exhibit globular guide surfaces 27, which permit the sliding element 23, and with it also the seat carrier 4 connected to the sliding element 23, to accompany the pivoting movement rearwards and downwards. The sliding element 23, which is executed in the form of a rail, in other words travels with its upper side 28 and its under side 29 along the guide surfaces 27 of the upper and lower sliding blocks 24, 25, in conjunction with which the sliding element 23 is guided reliably in any desired pivoting position between the upper and the lower sliding blocks 24, 25. This form of articulation can, of course, also be replaced by other types of articulation. The rotary sliding articulation described in published, non-prosecuted German patent application DE 101 25 994 A1 can be used, for example.

Because of the form of the backrest carrier 5 and its arrangement on the basic carrier 2 and the seat carrier 4, and when the backrest is subjected to loading, the backrest carrier 5 executes on the one hand a pivoting movement in the direction of pivoting S towards the rear and downwards. However, the pivoting movement also causes the seat carrier 4 both to be pivoted both towards the rear and downwards, and to be displaced horizontally rearwards in the area of the rotary sliding articulation 22. This does not produce any relevant lifting movement at the front end of the seat surface, as a result of which constrictions on the under side of the upper leg are avoided.

Compared with the solutions previously familiar from the state of the art, a pivoting mechanism of particularly simple construction is proposed in accordance with the invention. Manufacturing costs are reduced on the one hand in this way. On the other hand, the so-called “shirt-pulling-out effect” is also significantly reduced in this way, in spite of the simple configuration. To put it another way, particularly high seating comfort is achieved, but without having to resort to complicated and costly solutions.

In addition, the position of the seat carrier 4 in relation to the basic carrier 2 can be locked by a locking mechanism 30 in the area of the front end 21 of the seat carrier 4. The locking mechanism 30 contains, on the one hand, locking grooves 32 disposed one after the other in the longitudinal direction L on the under side 31 of the seat carrier 4, and, on the other hand, an substantially cuboid-shaped locking key 33 disposed in the basic carrier 2, which key is executed to engage in the locking grooves 32. The locking key 33 is guided in a guide channel 34 and is attached at its lower end to a wire spring 35, which is capable of being actuated via a pivot lever 36 in a manner not represented here in any greater detail. In the locked position, the locking key 33 is pretensioned by the wire spring 35 in the direction of the locking groove 32, so that secure engagement in the locking groove 32 is assured. By actuation of the pivot lever 36, the wire spring 35 is caused to move downwards, as a consequence of which the active return of the locking key 33 from the locked position takes place. A free end of the locking key exhibits a key end 37 with a mushroom-shaped cross section, by which it engages in the locking groove 32. The chamfered contact surfaces of the key end 37 also ensure secure locking in the locking groove 32 when the seat carrier 4 is caused to pivot.

A plurality of locking grooves 32 disposed one after the other in the longitudinal direction L are provided. The synchronizing mechanism can accordingly be secured in various intermediate positions between the basic position and the maximum, rearward-pivoted position. The operating lever 38 disposed opposite the pivot lever 36 is used to release the vertical adjustment of the chair upright.

The synchronizing mechanism 1 is pre-tensioned against the direction of pivoting S that is to say towards the basic position of the synchronizing mechanism 1. A spring configuration is provided in the form of two leg springs 41 capable of alignment with one another in a transverse direction; see FIG. 7. The leg springs 41, 41′ are positioned around the pivot shaft 14. An upward-facing leg 42 is supported against a projection on the seat carrier 4, whereas a second, forward-facing leg 43 is supported on an adjuster mechanism in the basic carrier 2. The leg springs 41, 41′ exert a spring force against the rearward-directed pivoting movement of the backrest, which is variable through the adjuster mechanism by actuation by a crank lever 44.

The adjustment mechanism contains a worm 46 connected via a shaft 45 to the crank lever 44, in conjunction with which the shaft 45 lies in bearing shells 47 in the basic carrier 2; see FIG. 6. The crank lever 44 is disposed in the sleeve-shaped pivot lever 38 for the release of the gas spring and is pulled out for actuation of the worm gear. The worm 46 engages with its teeth in a worm gear 48, which is connected to a threaded rod 49. The threaded rod 49 is mounted at both of its ends 52, 53 so that it is capable of rotating on the one hand in a cover 50 of the basic carrier 2 and on the other hand in a basic body 51 of the basic carrier 2. By actuation of the crank lever 44, the worm gear 48 is caused to rotate by the worm 46, and a guide prism 54 serving as a bearing for the spring leg is guided along the threaded rod 52 by the movement of the threaded rod 52. If the guide prism 54 is moved downwards, the forward-facing spring leg 43 of the leg spring 41 is acted upon and is forced downwards, which leads to an increase in the pre-tensioning of the leg spring 41. The consequence of this is that the pivoting movement of the seat carrier 4 and the backrest carrier 5 takes place in the direction of pivoting S against a greater resistance.

The upward-facing second leg 42 of the leg spring 41 makes contact with a second guide prism 55, which is disposed on the under side 31 of the seat carrier 4. In other words, the leg spring 41 is supported in a floating fashion on both sides. In the event of the pivoting of the seat carrier 4 rearwards and downwards, that is to say in the direction of pivoting S, the point of articulation of the upper spring leg 42 is displaced. The position of the point of articulation accordingly changes when a load is placed on the backrest in such a way that the point of articulation is displaced in the direction of the mid point 56 of the spring. The result of this is an automatic change in the spring behavior of the leg spring 41 in the event of a movement in the direction of pivoting S. To put it another way, in the event of pivoting of the seat, the leg spring 41, and thus the seat as a whole, automatically become harder.

The backrest carrier 5 is secured to the central pivot shaft 14 with fixing screws 57. During the pivoting movement, the pivot shaft 14 in other words rotates together with the backrest carrier 5. The diameter of the pivot shaft 14 is selected so that the leg springs 41, 41′ do not lie on the pivot shaft 14 in the tensioned position. The internal diameter of the leg springs 41, 41′ is at all times greater than the diameter of the pivot shaft 14. Unobstructed rotation of the pivot shaft 14 is assured in this way in conjunction with pivoting of the seat. In addition, disturbing contact noises such as creaking are avoided. However, since both of the leg springs 41, 41′ applied to the pivot shaft 14 lie with their periphery in a spring support 58 in the form of a prism, the positioning of the leg springs 41, 41′ in their operating position is still reliably assured.

The use of leg springs 41, 41′ permits the direct transmission of the spring force to the synchronizing mechanism 1, so that additional component parts are not required for the transmission of the force. The total number of component parts required is also smaller, when compared to the synchronizing mechanisms that are already familiar from the state of the art, since the adjusting mechanism is constructed from relatively few component parts. The adjusting mechanism is particularly robust, furthermore, due to the use of the worm drive, and because of its very high transmission ratio, it permits the particularly light adjustment of the crank lever.

An alternative embodiment (not shown here) provides for the seat carrier 4 to be integrated into the seat shell of the seat. In other words, the seat shell of the seat is executed in such a way that it is connected directly to the basic carrier 2. A separate seat carrier is then no longer necessary. The manufacturing costs can be further reduced in this way. Alongside the reduction in the required number of component parts, a reduction in the overall height is also possible. A more delicate form is imparted to the seat in this way. The backrest carrier 5 is attached in an articulated fashion directly to the rear end of the seat shell, and the basic carrier 2 is similarly connected to the front end of the seat shell via a sliding bearing or the like. The seat shell exhibits two pivot bearings to accommodate the pivot shaft 14. The sliding element 23 is also a component part of the seat shell. The pivot bearings and the sliding element 23 are preferably also an integral part of the seat shell. The seat shell similarly exhibits the locking grooves 32 necessary for the locking mechanism. 

1. A synchronizing mechanism for correlating a movement of a seat and a backrest assembly of an office chair, the synchronizing mechanism comprising: a seat carrier having a rear end area; a first transverse shaft; a basic carrier capable of being positioned on the office chair upright; a backrest carrier capable of pivoting about said transverse shaft and connected directly in an articulated fashion to said basic carrier and to said rear end area of said seat carrier such that a pivoting movement of said backrest carrier in a rearward direction will induce a lowering movement in said rear end area of said seat carrier; and a second transverse shaft; said seat carrier capable of pivoting about said second transverse shaft and connected directly to said basic carrier in an articulated fashion such that a horizontal sliding movement towards a rear being superimposed during the lowering movement of said seat carrier.
 2. The synchronizing mechanism according to claim 1, wherein in a basic position of the synchronizing mechanism, a ratio of a horizontal component of an articulation distance to a vertical component of the articulation distance lies between 0.6 and 1.7.
 3. The synchronizing mechanism according to claim 1, wherein in a maximum rearward-pivoted position of the synchronizing mechanism, a ratio of a horizontal component of an articulation distance to a vertical component of the articulation distance lies between 2.8 and 5.8.
 4. The synchronizing mechanism according to claim 3, wherein in the maximum rearward-pivoted position, a ratio of a lowering angle of said seat carrier to a pivoting angle of said backrest carrier lies between 1:2.1 and 1:3.0.
 5. The synchronizing mechanism according to claim 1, further comprising a rotary sliding articulation, said seat carrier having a front end area connected to said basic carrier through said rotary sliding articulation.
 6. The synchronizing mechanism according to claim 1: wherein said seat carrier has a front end area; and further comprising a locking mechanism provided in said front end area of said seat carrier for locking a position of said seat carrier in relation to said basic carrier.
 7. The synchronizing mechanism according to claim 1, wherein said seat carrier has a spring counterpart; and further comprising a spring configuration for pre-tensioning the synchronizing mechanism, said spring configuration containing a leg spring with a leg abutting against said spring counterpart disposed on said seat carrier such that a position of an articulation point, and thus a spring characteristic of said leg spring, being varied in conjunction with the pivoting of said backrest carrier.
 8. The synchronizing mechanism according to claim 7, wherein: said basic carrier has an adjustment mechanism with a worm gear for actuating said adjustment mechanism; and said leg spring having a further leg supported on said adjustment mechanism in said basic carrier.
 9. The synchronizing mechanism according to claim 1, wherein said seat carrier is a seat. 